Electrode configurations for leads or catheters to enhance localization using a localization system

ABSTRACT

An exemplary method includes positioning a lead in a patient where the lead has a longitudinal axis that extends from a proximal end to a distal end and where the lead includes an electrode with an electrical center offset from the longitudinal axis of the lead body; measuring electrical potential in a three-dimensional potential field using the electrode; and based on the measuring and the offset of the electrical center, determining lead roll about the longitudinal axis of the lead body where lead roll may be used for correction of field heterogeneity, placement or navigation of the lead or physiological monitoring (e.g., cardiac function, respiration, etc.). Various other methods, devices, systems, etc., are also disclosed.

TECHNICAL FIELD

Subject matter presented herein relates generally to localizationsystems and invasive therapies. Various examples pertain to lead-basedelectrodes that can enhance lead localization for placement, navigationor physiologic mapping. Such electrodes are optionally suited forsensing, stimulation or sensing and stimulation.

BACKGROUND

Various techniques exist to “image” internal physiology. Some of thesetechniques are considered “non-invasive”, for example, those that relyon penetration of sound (e.g., ultrasound), electromagnetic energy(e.g., MRI, CT) or particles (e.g., PET). However, when such techniquesrequire enhancement, clinicians often resort to intravenous delivery ofcontrast agents or dyes. For example, cardiac fluoroscopy can beenhanced through use of contrast agents or dyes delivered intravenouslyvia a catheter. Further, fluoroscopy also provides some degree ofvisualization, which can help a clinician navigate such a catheter in apatient's body.

Another non-invasive technique is often referred to as “electricalimpedance tomography” or “electrical capacitance tomography”. Suchtechniques are referred to herein as simply “electrical tomography”(ET). Conventional ET generates images of the body related to dielectricproperties and underlying physiology as reconstructed from skin-surfaceelectrical measurements. Typically, ET involves placing electrodes onthe skin and applying small alternating currents via some or all of theelectrodes. In turn, corresponding electrical potentials are measuredand processed to generate an image or images that represent theunderlying physiology.

An invasive variation of ET is referred to herein as ET localizationwhere one or more electrodes are introduced into the body and reliedupon for physiologic mapping or localization (e.g., via delivery ofelectrical potentials or current, measurement of potentials or current,etc.). A particular commercially available navigation and localizationsystem is marketed as the ENSITE® NAVX® system and technology (St. JudeMedical, Inc., Minnesota).

In a typical clinical application, the ENSITE® NAVX® system drivescurrent across three pairs of body surface patches to create a Cartesiancoordinate system in the body, in which indwelling electrodes may belocated in real-time. Potentials sensed by the indwelling electrodes inthe current fields can be used to compute impedances that determine aposition of each electrode (e.g., in three dimensions). In variousclinical applications, indwelling electrodes may be used to measurecardiac potentials and to deliver energy, for example to pace or toablate tissue. A computed position or positions of an indwellingelectrode or electrodes, in conjunction with the sensed electrograms andpossibly other information, can be used to generate maps that mayinclude anatomical features as well as information about tissuesubstrate and performance.

Various exemplary technologies described herein pertain to localization,navigation or both localization and navigation. Various examples aredescribed with respect to ET. As described in below, various exemplarytechnologies may be optionally suited or adapted for use with imagingmodalities such as MR, CT and ultrasound (e.g., ultrasound tomography,UT).

SUMMARY

An exemplary method includes positioning a lead in a patient where thelead has a longitudinal axis that extends from a proximal end to adistal end and where the lead includes an electrode with an electricalcenter offset from the longitudinal axis of the lead body; measuringelectrical potential in a three-dimensional potential field using theelectrode; and based on the measuring and the offset of the electricalcenter, determining lead roll about the longitudinal axis of the leadbody where lead roll may be used for correction of field heterogeneity,placement or navigation of the lead or physiological monitoring (e.g.,cardiac function, respiration, etc.). Various other methods, devices,systems, etc., are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the described implementations can be morereadily understood by reference to the following description taken inconjunction with the accompanying drawings.

FIG. 1 is a simplified diagram illustrating an exemplary implantablestimulation device in electrical communication with at least three leadsimplanted into a patient's heart and at least one other lead for sensingand/or delivering stimulation and/or shock therapy. Other devices withmore or fewer leads may also be suitable.

FIG. 2 is a functional block diagram of an exemplary implantablestimulation device illustrating basic elements that are configured toprovide cardioversion, defibrillation, pacing stimulation and/or othertissue stimulation. The implantable stimulation device is furtherconfigured to sense information and administer therapy responsive tosuch information.

FIG. 3 is a block diagram of an exemplary method for optimizing therapyand/or monitoring conditions based at least in part on positioninformation.

FIG. 4 is an exemplary arrangement of a lead and electrodes foracquiring position information and optionally other information.

FIG. 5 is a diagram illustrating field heterogeneities associated withcurrent generated fields in the body along with a method to compensatefor field heterogeneities.

FIG. 6 is a diagram illustrating a two lead scenario with respect to alocal coordinate system for each lead and a global coordinate system.

FIG. 7 is a diagram of a conventional lead with symmetric roll in alocal coordinate system and an exemplary lead with asymmetric roll in alocal coordinate system as well as an exemplary method for using theexemplary lead.

FIG. 8 is a diagram of an exemplary lead with twist tracking featuresalong with an exemplary method for using the exemplary lead.

FIG. 9 is a diagram of a conventional ring electrode and its electricalcenter and a pair of exemplary electrodes and corresponding individualelectrical centers.

FIG. 10 is a series of diagrams illustrating various exemplaryelectrodes with respect to a lead body.

FIG. 11 is a series of diagrams illustrating various exemplaryelectrodes with respect to a lead body.

FIG. 12 is a series of diagrams illustrating various exemplaryelectrodes with respect to a lead body.

FIG. 13 is a diagram of an exemplary localization system, exemplaryarrangement of leads in the heart and exemplary displays.

FIG. 14 is a diagram of an exemplary localization system, an exemplarymethod and an exemplary sequence of data entry.

FIG. 15 is an exemplary system for acquiring information and analyzingsuch information.

DETAILED DESCRIPTION

The following description includes the best mode presently contemplatedfor practicing the described implementations. This description is not tobe taken in a limiting sense, but rather is made merely for the purposeof describing the general principles of the implementations. The scopeof the described implementations should be ascertained with reference tothe issued claims. In the description that follows, like numerals orreference designators will be used to reference like parts or elementsthroughout.

Overview

As described herein, various exemplary electrodes and associatedtechniques can enhance localization for lead or electrode placement andnavigation or physiologic mapping. For example, an exemplary electrodearray and switching mechanism allows for sequential acquisition ofpotentials in a field generated by applied current. In such an example,the acquired potentials can be used to locate the array in a localcoordinate system (e.g., including yaw, pitch and roll) or to compensatefor field heterogeneities and thereby enhance location accuracy. Inanother example, an exemplary electrode array provides multiple,discrete electrical centers (e.g., geometric centers for electrodes ofsame characteristics), which may be selectable via a switchingmechanism. Various other examples are described below.

Exemplary Stimulation Device

The techniques described below may be implemented in connection with adevice configured or configurable to deliver cardiac therapy or tomonitor cardiac condition.

FIG. 1 shows an exemplary stimulation device 100 in electricalcommunication with a patient's heart 102 by way of three leads (a rightatrial lead 104, a left ventricular lead 106 and a right ventricularlead 108), suitable for delivering multi-chamber stimulation and shocktherapy. The leads 104, 106, 108 are optionally configurable fordelivery of stimulation pulses suitable for stimulation of nerves orother tissue. In addition, in the example of FIG. 1, the device 100includes a fourth lead 110 having multiple electrodes 144, 144′, 144″suitable for stimulation of tissue and/or sensing of physiologicsignals. This lead may be positioned in and/or near a patient's heartand/or remote from the heart.

FIG. 1 also shows approximate locations of the right and left phrenicnerves 154, 158. The phrenic nerve is made up mostly of motor nervefibres for producing contractions of the diaphragm. In addition, itprovides sensory innervation for various components of the mediastinumand pleura, as well as the upper abdomen (e.g., liver and gall bladder).The right phrenic nerve 154 passes over the brachiocephalic artery,posterior to the subclavian vein, and then crosses the root of the rightlung anteriorly and then leaves the thorax by passing through the venacava hiatus opening in the diaphragm at the level of T8. Morespecifically, with respect to the heart, the right phrenic nerve 154passes over the right atrium while the left phrenic nerve 158 passesover the pericardium of the left ventricle and pierces the diaphragmseparately. While certain therapies may call for phrenic nervestimulation (e.g., for treatment of sleep apnea), in general, cardiacpacing therapies avoid phrenic nerve stimulation through judicious leadand electrode placement, selection of electrode configurations,adjustment of pacing parameters, etc.

Referring again to the various leads of the device 100, the right atriallead 104, as the name implies, is positioned in and/or passes through apatient's right atrium. The right atrial lead 104 is configured to senseatrial cardiac signals and/or to provide right atrial chamberstimulation therapy. As described further below, the right atrial lead104 may be used by the device 100 to acquire far-field ventricularsignal data. As shown in FIG. 1, the right atrial lead 104 includes anatrial tip electrode 120, which typically is implanted in the patient'sright atrial appendage, and an atrial ring electrode 121. The rightatrial lead 104 may have electrodes other than the tip 120 and ring 121electrodes. Further, the right atrial lead 104 may include electrodessuitable for stimulation and/or sensing located on a branch.

To sense atrial cardiac signals, ventricular cardiac signals and/or toprovide chamber pacing therapy, particularly on the left side of apatient's heart, the stimulation device 100 is coupled to the leftventricular lead 106, which in FIG. 1 is also referred to as a coronarysinus lead as it is designed for placement in the coronary sinus and/ortributary veins of the coronary sinus. As shown in FIG. 1, the coronarysinus lead 106 is configured to position at least one distal electrodeadjacent to the left ventricle and/or additional electrode(s) adjacentto the left atrium. In a normal heart, tributary veins of the coronarysinus include, but may not be limited to, the great cardiac vein, theleft marginal vein, the left posterior ventricular vein, the middlecardiac vein, and the small cardiac vein.

In the example of FIG. 1, the coronary sinus lead 106 includes a seriesof electrodes 123. In particular, a series of four electrodes are shownpositioned in an anterior vein of the heart 102. Other coronary sinusleads may include a different number of electrodes than the lead 106. Asdescribed herein, an exemplary method selects one or more electrodes(e.g., from electrodes 123 of the lead 106) and determinescharacteristics associated with conduction and/or timing in the heart toaid in ventricular pacing therapy and/or assessment of cardiaccondition. As described in more detail below, an illustrative methodacquires information using various electrode configurations where anelectrode configuration typically includes at least one electrode of acoronary sinus lead or other type of left ventricular lead. Suchinformation may be used to determine a suitable electrode configurationfor the lead 106 (e.g., selection of one or more electrodes 123 of thelead 106).

In the example of FIG. 1, as connected to the device 100, the coronarysinus lead 106 is configured for acquisition of ventricular cardiacsignals (and optionally atrial signals) and to deliver left ventricularpacing therapy using, for example, at least one of the electrodes 123and/or the tip electrode 122. The lead 106 optionally allows for leftatrial pacing therapy, for example, using at least the left atrial ringelectrode 124. The lead 106 optionally allows for shocking therapy, forexample, using at least the left atrial coil electrode 126. For acomplete description of a particular coronary sinus lead, the reader isdirected to U.S. Pat. No. 5,466,254, “Coronary Sinus Lead with AtrialSensing Capability” (Helland), which is incorporated herein byreference.

The stimulation device 100 is also shown in electrical communicationwith the patient's heart 102 by way of an implantable right ventricularlead 108 having, in this exemplary implementation, a right ventriculartip electrode 128, a right ventricular ring electrode 130, a rightventricular (RV) coil electrode 132, and an SVC coil electrode 134.Typically, the right ventricular lead 108 is transvenously inserted intothe heart 102 to place the right ventricular tip electrode 128 in theright ventricular apex so that the RV coil electrode 132 will bepositioned in the right ventricle and the SVC coil electrode 134 will bepositioned in the superior vena cava. Accordingly, the right ventricularlead 108, as connected to the device 100, is capable of sensing orreceiving cardiac signals, and delivering stimulation in the form ofpacing and shock therapy to the right ventricle. An exemplary rightventricular lead may also include at least one electrode capable ofstimulating other tissue; such an electrode may be positioned on thelead or a bifurcation or leg of the lead. A right ventricular lead mayinclude a series of electrodes, such as the series 123 of the leftventricular lead 106.

FIG. 1 also shows a lead 160 as including several electrode arrays 163.In the example of FIG. 1, each electrode array 163 of the lead 160includes a series of electrodes 162 with an associated circuit 168.Conductors 164 provide an electrical supply and return for the circuit168. The circuit 168 includes control logic sufficient to electricallyconnect the conductors 164 to one or more of the electrodes of theseries 162. In the example of FIG. 1, the lead 160 includes a lumen 166suitable for receipt of a guidewire to facilitate placement of the lead160. As described herein, any of the leads 104, 106, 108 or 110 mayinclude one or more electrode array, optionally configured as theelectrode array 163 of the lead 160. For example, the lead 106 mayinclude features of the lead 160 and be suitable for multisite pacingfor cardiac resynchronization therapy (CRT).

FIG. 2 shows an exemplary, simplified block diagram depicting variouscomponents of the device 100. The device 100 can be capable of treatingboth fast and slow arrhythmias with stimulation therapy, includingcardioversion, defibrillation, and pacing stimulation. While aparticular multi-chamber device is shown, it is to be appreciated andunderstood that this is for illustration purposes only. Thus, thetechniques, methods, etc., described below can be implemented inconnection with any suitably configured or configurable device.Accordingly, one of skill in the art could readily duplicate, eliminate,or disable the appropriate circuitry in any desired combination toprovide a device capable of treating the appropriate chamber(s) orregions of a patient's heart.

Housing 200 for the device 100 is often referred to as the “can”, “case”or “case electrode”, and may be programmably selected to act as thereturn electrode for all “unipolar” modes. As described below, variousexemplary techniques implement unipolar sensing for data that mayinclude indicia of functional conduction block in myocardial tissue.Housing 200 may further be used as a return electrode alone or incombination with one or more of the coil electrodes 126, 132 and 134 forshocking or other purposes. Housing 200 further includes a connector(not shown) having a plurality of terminals 201, 202, 204, 206, 208,212, 214, 216, 218, 221, 223 (shown schematically and, for convenience,the names of the electrodes to which they are connected are shown nextto the terminals).

To achieve right atrial sensing, pacing and/or other tissue sensing,stimulation, etc., the connector includes at least a right atrial tipterminal (A_(R) TIP) 202 adapted for connection to the right atrial tipelectrode 120. A right atrial ring terminal (A_(R) RING) 201 is alsoshown, which is adapted for connection to the right atrial ringelectrode 121. To achieve left chamber sensing, pacing, shocking, and/orother tissue sensing, stimulation, etc., the connector includes at leasta left ventricular tip terminal (V_(L) TIP) 204, a left atrial ringterminal (A_(L) RING) 206, and a left atrial shocking terminal (A_(L)COIL) 208, which are adapted for connection to the left ventricular tipelectrode 122, the left atrial ring electrode 124, and the left atrialcoil electrode 126, respectively. Connection to suitable stimulationelectrodes is also possible via these and/or other terminals (e.g., viaa stimulation terminal S ELEC 221). The terminal S ELEC 221 mayoptionally be used for sensing. For example, electrodes of the lead 110may connect to the device 100 at the terminal 221 or optionally at oneor more other terminals.

A terminal 223 allows for connection of a series of left ventricularelectrodes. For example, the series of four electrodes 123 of the lead106 may connect to the device 100 via the terminal 223. The terminal 223and an electrode configuration switch 226 allow for selection of one ormore of the series of electrodes and hence electrode configuration. Inthe example of FIG. 2, the terminal 223 includes four branches to theswitch 226 where each branch corresponds to one of the four electrodes123.

As described herein, a terminal or terminals may allow for transmissionof information to a lead that includes a control circuit such as thelead 160 of FIG. 1. For example, a terminal may transmit a signal thatcauses the circuit 168 to select one or more of the electrodes 162 fordelivery of energy to the body, for sensing electrical activity of thebody or for delivery of energy and sensing activity.

To support right chamber sensing, pacing, shocking, and/or other tissuesensing, stimulation, etc., the connector further includes a rightventricular tip terminal (V_(R) TIP) 212, a right ventricular ringterminal (V_(R) RING) 214, a right ventricular shocking terminal (RVCOIL) 216, and a superior vena cava shocking terminal (SVC COIL) 218,which are adapted for connection to the right ventricular tip electrode128, right ventricular ring electrode 130, the RV coil electrode 132,and the SVC coil electrode 134, respectively.

At the core of the stimulation device 100 is a programmablemicrocontroller 220 that controls the various modes of cardiac or othertherapy. As is well known in the art, microcontroller 220 typicallyincludes a microprocessor, or equivalent control circuitry, designedspecifically for controlling the delivery of stimulation therapy, andmay further include RAM or ROM memory, logic and timing circuitry, statemachine circuitry, and I/O circuitry. Typically, microcontroller 220includes the ability to process or monitor input signals (data orinformation) as controlled by a program code stored in a designatedblock of memory. The type of microcontroller is not critical to thedescribed implementations. Rather, any suitable microcontroller 220 maybe used that is suitable to carry out the functions described herein.The use of microprocessor-based control circuits for performing timingand data analysis functions are well known in the art.

Representative types of control circuitry that may be used in connectionwith the described embodiments can include the microprocessor-basedcontrol system of U.S. Pat. No. 4,940,052, the state-machine of U.S.Pat. Nos. 4,712,555 and 4,944,298, all of which are incorporated byreference herein. For a more detailed description of the various timingintervals used within the stimulation device and theirinter-relationship, see U.S. Pat. No. 4,788,980, also incorporatedherein by reference.

FIG. 2 also shows an atrial pulse generator 222 and a ventricular pulsegenerator 224 that generate pacing stimulation pulses for delivery bythe right atrial lead 104, the coronary sinus lead 106, and/or the rightventricular lead 108 via an electrode configuration switch 226. It isunderstood that in order to provide stimulation therapy in each of thefour chambers of the heart (or to other tissue) the atrial andventricular pulse generators, 222 and 224, may include dedicated,independent pulse generators, multiplexed pulse generators, or sharedpulse generators. The pulse generators 222 and 224 are controlled by themicrocontroller 220 via appropriate control signals 228 and 230,respectively, to trigger or inhibit the stimulation pulses.

The microcontroller 220 further includes timing control circuitry 232 tocontrol the timing of the stimulation pulses (e.g., pacing rate,atrio-ventricular (AV) delay, interatrial conduction (AA) delay, orinterventricular conduction (VV) delay, etc.) as well as to keep trackof the timing of refractory periods, blanking intervals, noise detectionwindows, evoked response windows, alert intervals, marker channeltiming, etc., which is well known in the art.

The microcontroller 220 further includes an arrhythmia detector 234. Thedetector 234 can be utilized by the stimulation device 100 fordetermining desirable times to administer various therapies. Thedetector 234 may be implemented in hardware as part of themicrocontroller 220, or as software/firmware instructions programmedinto the device and executed on the microcontroller 220 during certainmodes of operation.

Microcontroller 220 further includes a morphology discrimination module236, a capture detection module 237 and an auto sensing module 238.These modules are optionally used to implement various exemplaryrecognition algorithms and/or methods presented below. Theaforementioned components may be implemented in hardware as part of themicrocontroller 220, or as software/firmware instructions programmedinto the device and executed on the microcontroller 220 during certainmodes of operation. The capture detection module 237, as describedherein, may aid in acquisition, analysis, etc., of information relatingto IEGMs and, in particular, act to distinguish capture versusnon-capture versus fusion.

The electronic configuration switch 226 includes a plurality of switchesfor connecting the desired electrodes to the appropriate I/O circuits,thereby providing complete electrode programmability. Accordingly,switch 226, in response to a control signal 242 from the microcontroller220, determines the polarity of the stimulation pulses (e.g., unipolar,bipolar, etc.) by selectively closing the appropriate combination ofswitches (not shown) as is known in the art.

Atrial sensing circuits 244 and ventricular sensing circuits 246 mayalso be selectively coupled to the right atrial lead 104, coronary sinuslead 106, and the right ventricular lead 108, through the switch 226 fordetecting the presence of cardiac activity in each of the four chambersof the heart. Accordingly, the atrial and ventricular sensing circuits,244 and 246, may include dedicated sense amplifiers, multiplexedamplifiers, or shared amplifiers. Switch 226 determines the “sensingpolarity” of the cardiac signal by selectively closing the appropriateswitches, as is also known in the art. In this way, the clinician mayprogram the sensing polarity independent of the stimulation polarity.The sensing circuits (e.g., 244 and 246) are optionally capable ofobtaining information indicative of tissue capture.

Each of the sensing circuits 244 and 246 preferably employs one or morelow power, precision amplifiers with programmable gain and/or automaticgain control, bandpass filtering, and a threshold detection circuit, asknown in the art, to selectively sense the cardiac signal of interest.The automatic gain control enables the device 100 to deal effectivelywith the difficult problem of sensing the low amplitude signalcharacteristics of atrial or ventricular fibrillation.

The outputs of the atrial and ventricular sensing circuits 244 and 246are connected to the microcontroller 220, which, in turn, is able totrigger or inhibit the atrial and ventricular pulse generators 222 and224, respectively, in a demand fashion in response to the absence orpresence of cardiac activity in the appropriate chambers of the heart.Furthermore, as described herein, the microcontroller 220 is alsocapable of analyzing information output from the sensing circuits 244and 246 and/or the data acquisition system 252 to determine or detectwhether and to what degree tissue capture has occurred and to program apulse, or pulses, in response to such determinations. The sensingcircuits 244 and 246, in turn, receive control signals over signal lines248 and 250 from the microcontroller 220 for purposes of controlling thegain, threshold, polarization charge removal circuitry (not shown), andthe timing of any blocking circuitry (not shown) coupled to the inputsof the sensing circuits, 244 and 246, as is known in the art.

For arrhythmia detection, the device 100 may utilize the atrial andventricular sensing circuits, 244 and 246, to sense cardiac signals todetermine whether a rhythm is physiologic or pathologic. Of course,other sensing circuits may be available depending on need and/or desire.In reference to arrhythmias, as used herein, “sensing” is reserved forthe noting of an electrical signal or obtaining data (information), and“detection” is the processing (analysis) of these sensed signals andnoting the presence of an arrhythmia or of a precursor or other factorthat may indicate a risk of or likelihood of an imminent onset of anarrhythmia.

The exemplary detector module 234, optionally uses timing intervalsbetween sensed events (e.g., P-waves, R-waves, and depolarizationsignals associated with fibrillation) and to perform one or morecomparisons to a predefined rate zone limit (i.e., bradycardia, normal,low rate VT, high rate VT, and fibrillation rate zones) and/or variousother characteristics (e.g., sudden onset, stability, physiologicsensors, and morphology, etc.) in order to determine the type ofremedial therapy (e.g., anti-arrhythmia, etc.) that is desired or needed(e.g., bradycardia pacing, anti-tachycardia pacing, cardioversion shocksor defibrillation shocks, collectively referred to as “tiered therapy”).Similar rules can be applied to the atrial channel to determine if thereis an atrial tachyarrhythmia or atrial fibrillation with appropriateclassification and intervention.

Cardiac signals are also applied to inputs of an analog-to-digital (A/D)data acquisition system 252. The data acquisition system 252 isconfigured to acquire intracardiac electrogram (IEGM) signals or otheraction potential signals, convert the raw analog data into a digitalsignal, and store the digital signals for later processing and/ortelemetric transmission to an external device 254. The data acquisitionsystem 252 is coupled to the right atrial lead 104, the coronary sinuslead 106, the right ventricular lead 108 and/or another lead (e.g., thelead 110) through the switch 226 to sample cardiac signals or othersignals across any pair or other number of desired electrodes. A controlsignal 256 from the microcontroller 220 may instruct the A/D 252 tooperate in a particular mode (e.g., resolution, amplification, etc.).

Various exemplary mechanisms for signal acquisition are described hereinthat optionally include use of one or more analog-to-digital converter.Various exemplary mechanisms allow for adjustment of one or moreparameter associated with signal acquisition.

The microcontroller 220 is further coupled to a memory 260 by a suitabledata/address bus 262, wherein the programmable operating parameters usedby the microcontroller 220 are stored and modified, as required, inorder to customize the operation of the stimulation device 100 to suitthe needs of a particular patient. Such operating parameters define, forexample, pacing pulse amplitude, pulse duration, electrode polarity,rate, sensitivity, automatic features, arrhythmia detection criteria,and the amplitude, waveshape, number of pulses, and vector of eachshocking pulse to be delivered to the patient's heart 102 within eachrespective tier of therapy. One feature of the described embodiments isthe ability to sense and store a relatively large amount of data (e.g.,from the data acquisition system 252), which data may then be used forsubsequent analysis to guide the programming and operation of the device100.

Advantageously, the operating parameters of the implantable device 100may be non-invasively programmed into the memory 260 through a telemetrycircuit 264 in telemetric communication via communication link 266 withthe external device 254, such as a programmer, transtelephonictransceiver, or a diagnostic system analyzer. The microcontroller 220activates the telemetry circuit 264 with a control signal 268. Thetelemetry circuit 264 advantageously allows intracardiac electrograms(IEGM) and other information (e.g., status information relating to theoperation of the device 100, etc., as contained in the microcontroller220 or memory 260) to be sent to the external device 254 through anestablished communication link 266.

The stimulation device 100 can further include one or more physiologicsensors 270. For example, the device 100 may include a “rate-responsive”sensor that may provide, for example, information to aid in adjustmentof pacing stimulation rate according to the exercise state of thepatient. However, the one or more physiological sensors 270 may furtherbe used to detect changes in cardiac output (see, e.g., U.S. Pat. No.6,314,323, entitled “Heart stimulator determining cardiac output, bymeasuring the systolic pressure, for controlling the stimulation”, toEkwall, issued Nov. 6, 2001, which discusses a pressure sensor adaptedto sense pressure in a right ventricle and to generate an electricalpressure signal corresponding to the sensed pressure, an integratorsupplied with the pressure signal which integrates the pressure signalbetween a start time and a stop time to produce an integration resultthat corresponds to cardiac output), changes in the physiologicalcondition of the heart, or diurnal changes in activity (e.g., detectingsleep and wake states). Accordingly, the microcontroller 220 responds byadjusting the various pacing parameters (such as rate, AV Delay, VVDelay, etc.) at which the atrial and ventricular pulse generators, 222and 224, generate stimulation pulses.

While shown as being included within the stimulation device 100, it isto be understood that one or more of the physiologic sensors 270 mayalso be external to the stimulation device 100, yet still be implantedwithin or carried by the patient. Examples of physiologic sensors thatmay be implemented in device 100 include known sensors that, forexample, sense respiration rate, oxygen concentration of blood, pH ofblood, CO₂ concentration of blood, ventricular gradient, cardiac output,preload, afterload, contractility, and so forth. Another sensor that maybe used is one that detects activity variance, wherein an activitysensor is monitored diurnally to detect the low variance in themeasurement corresponding to the sleep state. For a complete descriptionof the activity variance sensor, the reader is directed to U.S. Pat. No.5,476,483 which is hereby incorporated by reference.

The one or more physiologic sensors 270 optionally include sensors fordetecting movement and minute ventilation in the patient. Signalsgenerated by a position sensor, a MV sensor, etc., may be passed to themicrocontroller 220 for analysis in determining whether to adjust thepacing rate, etc. The microcontroller 220 may monitor the signals forindications of the patient's position and activity status, such aswhether the patient is climbing upstairs or descending downstairs orwhether the patient is sitting up after lying down.

The stimulation device 100 additionally includes a battery 276 thatprovides operating power to all of the circuits shown in FIG. 2. For thestimulation device 100, which employs shocking therapy, the battery 276is capable of operating at low current drains for long periods of time(e.g., preferably less than 10 μA), and is capable of providinghigh-current pulses (for capacitor charging) when the patient requires ashock pulse (e.g., preferably, in excess of 2 A, at voltages above 200V, for periods of 10 seconds or more). The battery 276 also desirablyhas a predictable discharge characteristic so that elective replacementtime can be detected.

The stimulation device 100 can further include magnet detectioncircuitry (not shown), coupled to the microcontroller 220, to detectwhen a magnet is placed over the stimulation device 100. A magnet may beused by a clinician to perform various test functions of the stimulationdevice 100 and/or to signal the microcontroller 220 that the externalprogrammer 254 is in place to receive or transmit data to themicrocontroller 220 through the telemetry circuits 264.

The stimulation device 100 further includes an impedance measuringcircuit 278 that is enabled by the microcontroller 220 via a controlsignal 280. The known uses for an impedance measuring circuit 278include, but are not limited to, lead impedance surveillance during theacute and chronic phases for proper lead positioning or dislodgement;detecting operable electrodes and automatically switching to an operablepair if dislodgement occurs; measuring respiration or minuteventilation; measuring thoracic impedance for determining shockthresholds; detecting when the device has been implanted; measuringstroke volume; and detecting the opening of heart valves, etc. Theimpedance measuring circuit 278 is advantageously coupled to the switch226 so that any desired electrode may be used.

In the case where the stimulation device 100 is intended to operate asan implantable cardioverter/defibrillator (ICD) device, it detects theoccurrence of an arrhythmia, and automatically applies an appropriatetherapy to the heart aimed at terminating the detected arrhythmia. Tothis end, the microcontroller 220 further controls a shocking circuit282 by way of a control signal 284. The shocking circuit 282 generatesshocking pulses of low (e.g., up to 0.5 J), moderate (e.g., 0.5 J to 10J), or high energy (e.g., 11 J to 40 J), as controlled by themicrocontroller 220. Such shocking pulses are applied to the patient'sheart 102 through at least two shocking electrodes, and as shown in thisembodiment, selected from the left atrial coil electrode 126, the RVcoil electrode 132, and/or the SVC coil electrode 134. As noted above,the housing 200 may act as an active electrode in combination with theRV electrode 132, or as part of a split electrical vector using the SVCcoil electrode 134 or the left atrial coil electrode 126 (i.e., usingthe RV electrode as a common electrode).

Cardioversion level shocks are generally considered to be of low tomoderate energy level (so as to minimize pain felt by the patient),and/or synchronized with an R-wave and/or pertaining to the treatment oftachycardia. Defibrillation shocks are generally of moderate to highenergy level (e.g., corresponding to thresholds in the range ofapproximately 5 J to 40 J), delivered asynchronously (since R-waves maybe too disorganized), and pertaining exclusively to the treatment offibrillation. Accordingly, the microcontroller 220 is capable ofcontrolling the synchronous or asynchronous delivery of the shockingpulses.

As already mentioned, the implantable device 100 includes impedancemeasurement circuitry 278. Such a circuit may measure impedance orelectrical resistance through use of various techniques. For example,the device 100 may deliver a low voltage (e.g., about 10 mV to about 20mV) of alternating current between the RV tip electrode 128 and the caseelectrode 200. During delivery of this energy, the device 100 maymeasure resistance between these two electrodes where the resistancedepends on any of a variety of factors. For example, the resistance mayvary inversely with respect to volume of blood along the path.

In another example, resistance measurement occurs through use of a fourterminal or electrode technique. For example, the exemplary device 100may deliver an alternating current between one of the RV tip electrode128 and the case electrode 200. During delivery, the device 100 maymeasure a potential between the RA ring electrode 121 and the RV ringelectrode 130 where the potential is proportional to the resistancebetween the selected potential measurement electrodes.

With respect to two terminal or electrode techniques, where twoelectrodes are used to introduce current and the same two electrodes areused to measure potential, parasitic electrode-electrolyte impedancescan introduce noise, especially at low current frequencies; thus, agreater number of terminals or electrodes may be used. For example,aforementioned four electrode techniques, where one electrode pairintroduces current and another electrode pair measures potential, cancancel noise due to electrode-electrolyte interface impedance.Alternatively, where suitable or desirable, a two terminal or electrodetechnique may use larger electrode areas (e.g., even exceeding about 1cm²) and/or higher current frequencies (e.g., above about 10 kHz) toreduce noise.

Various exemplary electrodes and associated techniques can enhancelocalization for lead or electrode placement and navigation orphysiologic mapping. With respect to the ENSITE® NAVX® localizationsystem, heterogeneities in a current generated field can introduceerrors in locating an electrode. In general, such a localization systemlocates the “electrical center” of an electrode, which is, in mostsituations, equivalent to the electrode's geometric center. Thus, aselectrode size increases, an electrode will occupy a larger portion of afield and likely be exposed to more field heterogeneity. Consequently, alarge electrode will be at greater risk of being inaccurately located bysuch a localization system. For a small electrode, a risk exists that itwill be located entirely in a heterogeneous portion of a field, whichcan give rise to an inaccurate position determination.

Various exemplary electrodes and associated switching mechanisms or moregenerally acquisition mechanisms can measure or uncover fieldheterogeneities and thereby enhance location accuracy of a localizationsystem. Further, various exemplary electrodes may be shaped to havegeometric centers that are “asymmetric” along one or more axes (or axesof rotation). Yet further, various exemplary electrodes may be arrangedas arrays where acquisition or processing of acquired informationprovides an indication of electrode or lead direction. Additionally,where dimensions of an electrode or an electrode array are known, thedimensions may be used to map field heterogeneities and ultimatelycompensate for such heterogeneities to improve accuracy of positiondeterminations.

The ENSITE® NAVX® localization system includes a feature called “FieldScaling” that measures local variations point-by-point based on a knowndistance between electrodes on a lead and applies correction factors forthese local variations, for example, to more accurately display anatomicfeatures and electrode positions. Various exemplary technologiesdescribed herein can operate in conjunction with this feature to enhanceperformance of the localization system for position and motion ofelectrodes, for display of anatomy or for computation of motion-basedhemodynamic surrogates.

FIG. 3 shows an exemplary method 300 for acquiring and analyzingposition information using a catheter or a lead with a specializedelectrode or electrodes. In the description that follows, the term“lead” is used, at times, to include “catheter”. In the example of FIG.3, the method 300 includes a configurations block 310 that includesintraoperative configurations 312 (e.g., acute configurations) andchronic configurations 314. The intraoperative configurations 312pertain to configurations that may be achieved during an operativeprocedure. For example, during an operative procedure, one or more leadsmay be positioned in a patient where the one or more leads are connectedto, or variously connectable to, a device configured to acquireinformation and optionally to deliver electrical energy to the patient(e.g., to the heart, to a nerve, to other tissue, etc.). The chronicconfigurations 314 pertain to configurations achievable by a chronicallyimplanted device and its associated lead or leads, or more generally,its electrode arrangements. In general, intraoperative configurationsinclude those achievable by physically re-positioning a lead in apatient's body while chronic configurations normally do not allow forre-positioning as a lead or leads are usually anchored duringimplantation or become anchored in the weeks to months afterimplantation. Chronic configurations do, however, include selection of asubset of the multiple implanted electrodes, for example using a distaltip electrode versus a less distal electrode as a cathode or using thedistal electrode and the less distal electrode as a bipolar pair versususing these electrodes as two independent cathodes (e.g., as independentunipolar configurations). Thus, intraoperative configurations includeconfigurations available by changing device settings, electrodeselection, and physical position of electrodes, while chronicconfigurations include only those configurations available by changingdevice settings and electrode selection, or “electronic repositioning”of one or more stimulation electrodes.

As indicated in FIG. 3, an acquisition block 320 includes acquisition ofposition information 322 and optionally acquisition of other information324 (e.g., electrical information as to field homogeneity orheterogeneity, electrical activity of the heart, biosensor information,etc.). While an arrow indicates that a relationship or relationships mayexist between the configurations block 310 and the acquisition block320, acquisition of information may occur by using in part an electrode(or other equipment) that is not part of a configuration. For example,the acquisition block 320 may rely on one or more surface electrodesthat define a coordinate system or location system for locating anelectrode that defines one or more configurations. For example, threepairs of surface electrodes positioned on a patient may be configured todeliver current and define a three-dimensional space whereby measurementof a potential locates an electrode or electrodes in thethree-dimensional space.

As described herein, an electrode may be configured for delivery ofenergy to the heart; for acquisition of electrical information; foracquisition of position information; for acquisition of electricalinformation and position information; for delivery of energy to theheart and for acquisition of electrical information; for delivery ofenergy to the heart and for acquisition of position information; fordelivery of energy to the heart, for acquisition of electricalinformation and for acquisition of position information.

In various examples, acquisition of position information occurs bymeasuring one or more potentials where the measuring relies on anelectrode or electrodes that may also be configured to deliver energy tothe heart (e.g., electrical energy to pace a chamber of the heart). Insuch a scenario, the electrode may deliver energy sufficient tostimulate the heart and then be tracked along one or more dimensions tomonitor the positional consequences of the stimulation. Further, such anelectrode or electrodes may be used to acquire electrical information(e.g., an IEGM that evidences an evoked response). Such an electrode orelectrodes can perform all three of these tasks with proper circuitryand control. For example, after delivery of the energy, an electrode maybe configured for acquiring one or more potentials related to locationand for acquiring an electrogram. To acquire potentials and anelectrogram, circuitry may include gating or other sampling techniques(e.g., to avoid circuitry or interference issues). Such circuitry mayrely on one sampling frequency for acquiring potentials for motiontracking and another sampling frequency for acquiring an electrogram.

The method 300 of FIG. 3 includes a determination block 330 fordetermining one or more of cardiac position 332, respiratory position334 (e.g., position in the body as affected by respiration), electrodeposition 336 and lead position 338.

As shown in the example of FIG. 3, the conclusion block 340 may performactions such as to optimize therapy 342 and/or to monitor patient and/ordevice condition 344. Information 320 or determinations 330 may bemapped or otherwise displayed with respect to anatomical features ormarkers. For example, as described herein, the determinations as toelectrode position 336 can be used to map field heterogeneities in amultidimensional field and to compensate for such heterogeneities toimprove accuracy of future position determinations. While electricalimpedance tomography relies on heterogeneities to image internalphysiology, various techniques described herein measure heterogeneitiesin a field and compensate for such heterogeneities to increase accuracyof position determinations.

As described herein, an exemplary method can include: positioning one ormore electrodes within the heart and/or surrounding space (e.g.,intra-chamber, intra-vascular, intrapericardial, etc., which may becollectively referred to as “cardiac space”); and acquiring information(e.g., via one or more measured potentials) to determine a location,locations or displacement for at least one of the one or more electrodesusing a localization system (e.g., the ENSITE® NAVX® system or othersystem with appropriate features). In such a method, the positionedelectrodes may be configured for acquisition of electrical information(e.g., IEGMs). Further, with respect to acquisition of information, anacquisition system may operate at an appropriate sampling rate. Forexample, an acquisition system for position information may operate at asampling rate of about 100 Hz (e.g., the ENSITE® NAVX® system can sampleat about 93 Hz) and an acquisition system for electrical information mayoperate at a sampling rate of about 1200 Hz (e.g., in unipolar, bipolaror other polar arrangement).

Further, for an electrode array or series of electrodes, an offset orinterleaving technique may be applied to acquire information fromindividual electrodes or groups of electrodes. A localization system orlead system may include a parallel interface, a serial interface or aparallel interface and a serial interface. Multiplexers or the like maybe configured as a switch for an acquisition channel or channels. Asexplained with respect to the lead 160 of FIG. 1, one or more smallscale circuits may be integrated into a lead (e.g., along a lead body, alead connector or at or near an electrode array). For example, anapplication-specific integrated circuit (ASIC) may be provided forselectable acquisition of information from one or more electrodes or fordelivery of energy by one or more electrodes. Small-scale multiplexers(MUX), including amplifiers, buffers, timers and the like, arecommercially available and may be suitable for use with exemplaryelectrodes described herein.

An exemplary method may include preparing a patient for both implant ofa device such as the device 100 of FIGS. 1 and 2 and for study using alocalization system. Such preparation may occur in a relatively standardmanner for implant prep, and using the ENSITE® NAVX® system or othersimilar technology. As described herein, any of a variety ofelectroanatomic mapping or localization systems that can locateindwelling electrodes in and around the heart may be used.

Once prepped, a clinician or robot may place leads and/or catheters inthe patient's body, including any leads to be chronically implanted aspart of a CRT system, as well as optional additional electrodes that mayyield additional information (e.g., to increase accuracy by providingglobal information or other information).

After an initial placement of an electrode-bearing catheter or anelectrode-bearing lead, a clinician may then connect one or moreelectrodes to an electroanatomic mapping or localization system. Theterm “connection” can refer to physical electrical connection orwireless connection (e.g., telemetric, RF, ultrasound, etc.) with theelectrodes or wireless connection with another device that is inelectrical contact with the electrodes.

Once an appropriate connection or connections have been made, real-timeposition data for one or more electrodes may be acquired for variousconfigurations or conditions. For example, position data may be acquiredduring normal sinus rhythm; pacing in one or more chambers; advancing,withdrawing, or moving a location of an electrode; pacing one or moredifferent electrode configurations (e.g. multisite pacing); or varyinginter-stimulus timing (e.g. AV delay, VV delay).

In various examples, simultaneous to the acquisition of positioninformation, an intracardiac electrogram (IEGM) from each electrode canalso be acquired and associated with the anatomic position of theelectrode. While various examples refer to simultaneous acquisition,acquisition of electrical information and acquisition of mechanicalinformation may occur sequentially (e.g., alternate cardiac cycles) orinterleaved (e.g., both acquired during the same cardiac cycle butoffset by sampling time or sampling frequency).

In various exemplary methods, electrodes within the cardiac space may beoptionally positioned at various locations (e.g., by continuous movementor by discrete, sequential moves), with a mapping system recording thereal-time motion information at each electrode position in apoint-by-point manner. Such motion data can by associated with arespective anatomic point from which it was collected. By moving theelectrodes from point to point during an intervention, the motion datafrom each location can be incorporated into a single map, model, orparameter.

An exemplary method may include determining one or more parameters wherean algorithm or a clinician may select a configuration (e.g., electrodelocation, multisite arrangement, AV/VV timing) that yielded the bestvalue for one or more parameters of a CRT system and use the selectedconfiguration as a chronic configuration for the CRT system. Such achronic configuration may be optionally updated from time to time (e.g.,during a follow-up visit, in a patient environment, etc., depending onspecific capabilities of a system).

Various exemplary methods, using either a single parameter or acombination of more than one parameter, may automatically select aconfiguration, present an optimal configuration for acknowledgement by aclinician, or present various configurations to a clinician along withpros and cons of each configuration (e.g., in objective or subjectiveterms). For example, a particular configuration may be associated with ahigh power usage that may excessively drain a power source of animplantable device (e.g., device battery 276). Other pros and cons maypertain to patient comfort (e.g., pain, lack of pain, overall feeling,etc.).

An exemplary method may rely on certain equipment at time of implant orexploration and other equipment after implantation of a device todeliver a cardiac therapy. For example, during an intraoperativeprocedure, wireless communication may not be required; whereas, during afollow-up visit, measured potentials for position of chronicallyimplanted electrodes and of measured IEGMs using chronically implantedelectrodes may be communicated wirelessly from an implanted device to anexternal device. With respect to optimization of a chronically implantedsystem, in general, electrode location will not be altered, but otherparameters altered to result in an optimal configuration (e.g., single-or multi-site arrangement, polarity, stimulation energy, timingparameters, etc.).

As discussed herein, various exemplary techniques deliver current andmeasure potential where potential varies typically with respect tocardiac mechanics (e.g., due to motion). For example, electrodes fordelivery of current may be placed at locations that do not varysignificantly with respect to cardiac mechanics while one or moreelectrodes for measuring potential may be placed at a location orlocations that vary with respect to cardiac mechanics. Alternatively,electrodes for measuring potential may be placed at locations that donot vary significantly with respect to cardiac mechanics while one ormore electrodes for delivery of current may be placed at a location orlocations that vary with respect to cardiac mechanics. Variouscombinations of the foregoing arrangements are possible as well.Electrodes may be associated with a catheter or a lead. In someinstances, an electrode may be a “stand-alone” electrode, such as a caseelectrode of an implantable device (see, e.g., the case electrode 200 ofthe device 100 of FIGS. 1 and 2).

In accordance with the method 300 of FIG. 3, an exemplary method mayinclude preparing a patient for both implant and a localization study.In this example, preparation can be accomplished in standard manner forimplant preparation and the mapping may rely on a localization systemsuch as the ENSITE® NAVX® system or other similar technology for themapping prep. After preparing the patient, the method includes placingleads and/or catheters in the patient's body, including any leads to bechronically implanted as part of a therapeutic system. After placement,the method includes connecting electrodes on leads and/or catheters tothe localization system (e.g., an electroanatomic mapping system). Withrespect to the term “connecting”, depending on the equipment, it mayinclude physical electrical connecting and/ortelemetric/RF/wireless/ultrasound/other communication connecting (e.g.,directly or indirectly, via another “bridging” device, with theelectrodes.)

After appropriate connections are made, acquiring or recording followsto record real-time positions of one or more electrodes for variousconfigurations or conditions such as, but not limited to: normal sinusrhythm; pacing in one or more chambers (e.g., RV pacing, LV pacing BiVpacing); at various lead placement locations, (i.e., advancing,withdrawing, or moving the location of an electrode); pacing one or moredifferent electrode configurations (e.g. multisite pacing); or varyinginter-stimulus timing (e.g. AV delay, VV delay). After or duringacquisition, the method can determine positions for one or moreelectrodes. Subsequently, based on the positions, optionally inconjunction with other information (e.g., other ENSITE® real-timecardiac performance parameters), a clinician or a device may select aconfiguration (e.g., electrode location, multisite configuration, AV/VVdelays, etc.) that yielded or yields the best value(s) for a mechanicaldyssynchrony parameter(s). This configuration may then be usedchronically (e.g., as the final configuration of a CRT setup).

Such a method may separately be implemented at a clinic or hospitalfollow-up after the time of implant, provided wireless communicationwith the chronic indwelling electrodes. In general, it can be assumedthat the electrode location will not be altered, but optimization ofsingle- or multi-site configuration as well as timing parameter maystill be performed.

FIG. 4 shows an arrangement and method 400 that may rely in part on acommercially available system marketed as ENSITE® NAVX® localizationsystem (see also LOCALISA® system, Medtronic, Inc., Minnesota). TheENSITE® NAVX® system is a computerized storage and display system foruse in electrophysiology studies of the human heart. The system consistsof a console workstation, patient interface unit, and anelectrophysiology mapping catheter and/or surface electrode kit. Byvisualizing the global activation pattern seen on color-codedisopotential maps in the system, in conjunction with the reconstructedelectrograms, an electrophysiologist can identify the source of anarrhythmia and can navigate to a defined area for therapy. The ENSITE®system is also useful in treating patients with simpler arrhythmias byproviding non-fluoroscopic navigation and visualization of conventionalelectrophysiology (EP) catheters.

As shown in FIG. 4, electrodes 432, 432′, which may be part of astandard EP catheter 430 (or lead), sense electrical potentialassociated with current signals transmitted between three pairs ofsurface electrode patches 422, 422′ (X-axis), 424, 424′ (Y-axis) and426, 426′ (Z-axis). An addition electrode patch 428 is available forreference, grounding or other function. The ENSITE® NAVX® system canalso collect electrical data from a catheter and can plot a cardiacelectrogram from a particular location (e.g., cardiac vein 103 of heart102). Information acquired may be displayed as a 3-D isopotential mapand as virtual electrograms. Repositioning of the catheter allows forplotting of cardiac electrograms from other locations. Multiplecatheters may be used as well. A cardiac electrogram orelectrocardiogram (ECG) of normal heart activity (e.g., polarization,depolarization, etc.) typically shows atrial depolarization as a “Pwave”, ventricular depolarization as an “R wave”, or QRS complex, andrepolarization as a “T wave”. The ENSITE® NAVX® system may useelectrical information to track or navigate movement and constructthree-dimensional (3-D) models of a chamber of the heart.

A clinician can use the ENSITE® NAVX® system to create a 3-D model of achamber in the heart for purposes of treating arrhythmia (e.g.,treatment via tissue ablation). To create the 3-D model, the clinicianapplies surface patches to the body. The ENSITE® NAVX® system transmitsan electrical signal between the patches and the system then senses theelectrical signal using one or more catheters positioned in the body.The clinician may sweep a catheter with electrodes across a chamber ofthe heart to outline structure. Signals acquired during the sweep,associated with various positions, can then be used to generate a 3-Dmodel. A display can display a diagram of heart morphology, which, inturn, may help guide an ablation catheter to a point for tissueablation.

With respect to the foregoing discussion of current delivery andpotential measurement, per a method 440, a system (e.g., such as theENSITE® NAVX® system) delivers low level separable currents from thethree substantially orthogonal electrode pairs (422, 422′, 424, 424′,426, 426′) positioned on the body surface (delivery block 442) andoptionally the electrode 428 (or one or more other electrodes). Thespecific position of a catheter (or lead) electrode within a chamber ofthe heart can then be established based on three resulting potentialsmeasured between the recording electrode with respect to a referenceelectrode, as seen over the distance from each patch set to therecording tip electrode (measurement block 444). Sequential positioningof a catheter (or lead) at multiple sites along the endocardial surfaceof a specific chamber can establish that chamber's geometry, i.e.,position mapping (position/motion mapping block 446). Where the catheter(or lead) 430 moves, the method 440 may also measure motion.

In addition to mapping at specific points, the ENSITE® NAVX® systemprovides for interpolation (mapping a smooth surface) onto whichactivation voltages and times can be registered. Around 50 points arerequired to establish a surface geometry and activation of a chamber atan appropriate resolution. The ENSITE® NAVX® system also permits thesimultaneous display of multiple catheter electrode sites, and alsoreflects real-time motion of both ablation catheters and thosepositioned elsewhere in the heart.

The ENSITE® NAVX® system relies on catheters for temporary placement inthe body. Various exemplary techniques described herein optionally useone or more electrodes for chronic implantation. Such electrodes may beassociated with a lead, an implantable device, or other chronicallyimplantable component. Referring again to FIG. 3, the configurationblock 310 indicates that intraoperative configurations 312 and chronicconfigurations 314 may be available. Intraoperative configurations 312may rely on a catheter and/or a lead suitable for chronic implantation.

With respect to motion, the exemplary system and method 400 may trackmotion of an electrode in one or more dimensions. For example, a plot450 of motion versus time for three dimensions corresponds to motion ofone or more electrodes of the catheter (or lead) 430 positioned in avessel 103 of the heart 102 where the catheter (or lead) 430 includesthe one or more electrodes 432, 432′. Two arrows indicate possiblemotion of the catheter (or lead) 430 where hysteresis may occur over acardiac cycle. For example, a systolic path may differ from a diastolicpath. An exemplary method may analyze hysteresis for any of a variety ofpurposes including selection of a stimulation site, selection of asensing site, diagnosis of cardiac condition, etc.

The exemplary method 440, as mentioned, includes the delivery block 442for delivery of current, the measurement block 444 to measure potentialin a field defined by the delivered current and the mapping block 446 tomap motion based at least in part on the measured potential. Accordingto such a method, motion during systole and/or diastole may beassociated with electrical information. Alone, or in combination withelectrical information, the mechanical motion information may be usedfor selection of optimal stimulation site(s), determination ofhemodynamic surrogates (e.g., surrogates to stroke volume,contractility, etc.), optimization of CRT, placement of leads,determination of pacing parameters (AV delay, VV delay, etc.), etc.

The system 400 may use one or more features of the aforementionedENSITE® NAVX® system. For example, one or more pairs of electrodes (422,422′, 424, 424′, 426, 426′) may be used to define one or more dimensionsby delivering an electrical signal or signals to a body and/or bysensing an electrical signal or signals. Such electrodes (e.g., patchelectrodes) may be used in conjunction with one or more electrodespositioned in the body (e.g., the electrodes 432, 432′).

The exemplary system 400 may be used to track motion of one or moreelectrodes due to systolic motion, diastolic motion, respiratory motion,etc. Electrodes may be positioned along the endocardium and/orepicardium during a scouting or mapping process for use in conjunctionwith electrical information. Such information may also be used alone, orin conjunction with electrical information, for identifying the optimallocation of an electrode or electrodes for use in delivering CRT. Forexample, a location may be selected for optimal stimulation, for optimalsensing, or other purposes (e.g., anchoring ability, etc.).

With respect to stimulation, stimulation may be delivered to controlcardiac mechanics (e.g., contraction of a chamber of the heart) andmotion information may be acquired where the motion information isassociated with the controlled cardiac mechanics. An exemplary selectionprocess may identify the best stimulation site based on factors such aselectrical activity, electromechanical delay, extent of motion,synchronicity of motion where motion may be classified as systolicmotion or diastolic motion. In general, motion information correspondsto motion of an electrode or electrodes (e.g., endocardial electrodes,epicardial electrodes, etc.) and may be related to motion of the heart.

FIG. 5 shows a field compensation scheme 500 for a localization system.As mentioned, the ENSITE® NAVX® system includes a feature known as“field scaling”, which may operate according to the scheme 500. Asdescribed herein, exemplary electrodes can enhance mapping of fieldheterogeneities and increase accuracy of position determinations (e.g.,via compensation techniques).

A diagram of field heterogeneity 510 shows a cross-section between theY-axis patches 424, 424′. Internal physiology and accompanyingdielectric properties introduce field heterogeneities. Further, asphysiology changes with respect to time due to cardiac function,respiration, patient position, etc., heterogeneities vary with respectto time as well.

An exemplary compensation method 560 commences in a positioning block562 that positions at least two electrodes. A measurement block 564measures potential for each of the electrodes. A comparison block 566follows that includes measuring or otherwise providing for a distance orangle between the at least two electrodes. For example, an electrode maybe considered a fiducial and spacing between two or more electrodesknown a priori. In an alternative example, a lead may have fiducialswith known spacing that are visible via x-ray imaging along with theelectrodes. In such an example, a clinician may simply count the numberof fiducials between electrodes. In yet another example, one or moreanatomical features may be relied upon to establish a distance that canbe used to infer a distance between two electrodes. Of course,combinations of such techniques may be used.

According to the method 560, a determination block 568 determineswhether and to what extent the field is heterogeneous. For example, if aknown distance between two electrodes is 5 mm and the current generatedfield is expected to have a particular field gradient over a distance of5 mm, then the potentials can be analyzed to determine if the fieldgradient differs from its expected field gradient. Given an appropriatenumber of determinations, a generation block 570 generates a fieldcompensation transform, algorithm, map, table or the like. The method560 then proceeds to an acquisition block 572 that acquires potentialsand compensates accordingly for field heterogeneities to provide moreaccurate position information.

When a localization system is configured to define one or moreelectrodes as belonging to a single lead or catheter, such a system maydisplay a “tube” that represents the lead body between two electrodes.In the ENSITE® NAVX® system, this display, however, is simply graphicaland represented as a straight line, a polynomial, or a spline. As such,it does not truly represent the trajectory or orientation of a lead bodyin the heart.

As described herein, various exemplary electrodes allow fordetermination of trajectory or orientation of an electrode, an electrodearray, a lead body or a portion of a lead body. Such electrodes canallow a localization system to determine not only the position of anelectrode but also its orientation, which can enhance the representationof a lead, enhance computed parameters related to the motion of anelectrode or lead, etc.

FIG. 6 shows an exemplary two lead scenario 600 along with localcoordinate systems for each of the leads 610, 630. In the example ofFIG. 6, electrodes on the leads 610, 630 are conventional ringelectrodes, which fail to yield rich positional information in the localcoordinate systems.

In FIG. 6, the two local coordinate systems (x, y, z and x′, y′, z′dimensions) are shown along with a global coordinate system (X, Y, Zdimensions). While Cartesian coordinates are shown in the example ofFIG. 6, other coordinate systems may be utilized.

The leads 610, 630 include two electrodes defined with respect to az-axis: z(n) and z(n−1) with a separation of Δz. In the local coordinatesystems, the leads 610, 630 may yaw, pitch or roll. Yaw involvesrotation about the y-axis, pitch involves rotation about the x-axis androll involves rotation about the z-axis.

If the lead is viewed as a vehicle in the body, yaw is lateralrotational or oscillatory movement of the vehicle about its verticalaxis. Given this vehicle analogy, pitch is movement about an axis thatis perpendicular to the vehicle's longitudinal axis and horizontal withrespect to its primary body. Pitch attitude is the orientation of thevehicle with respect to the pitch axis. The pitching moment is therising and falling of the vehicle's nose. When the nose rises, thepitching moment is positive; when the nose drops, the pitching moment isnegative and is also called a diving moment. As for roll, it representsmotion of the vehicle about its longitudinal, or nose-tail, axis.

The exemplary local coordinate systems approach of FIG. 6 can assist innavigation of a lead in a patient's body. Further, an analogy to vehiclemotion facilitates implementation of automated or assisted navigationcontrol (e.g., 3-D robotic control in conjunction with a localizationsystem).

As mentioned, the ring electrodes, having a symmetric axis or rotationabout the z-axis cannot readily provide for orientation of the lead 610or the lead 630. To demonstrate this point, FIG. 7 shows a diagram of aconventional lead with symmetric roll 710 and an exemplary lead withasymmetric roll 720 as well as an exemplary method 750 for using thelead 720. The exemplary lead 720 includes two electrodes that are shapedand positioned like opposing boiler plates but offset along the z-axis.Further, the electrical center of each electrode is offset from thez-axis (e.g., as shown, +/−x-axis). Thus, lead roll causes theelectrical centers of the electrodes to move in the x,y-plane, which,given a surrounding field of a localization system, will result inchanging positions of the two electrodes (see, e.g., electrical centersin example 930 of FIG. 9).

The exemplary method 750 includes a positioning block 752 where aclinician positions a lead such as the lead 720 in a patient's body. Forexample, the clinician may position a lead in a patient where the leadhas a longitudinal axis that extends from a proximal end to a distal endand where the lead includes an electrode with an electrical centeroffset from the longitudinal axis of the lead body. After or duringpositioning, in a measurement block 754, the clinician instructs alocalization system to measure electrical potential in athree-dimensional potential field using the electrode. In adetermination block 756, a localization system determines, based onmeasured electrical potential and the offset of the electrical center,lead roll about the longitudinal axis of the lead body (e.g., indegrees, radians, etc.). As described herein, an exemplary method caninclude displaying a lead roll indicator on a display, for example,where the lead roll indicator indicates degrees of roll about alongitudinal axis of a lead body. Such a method may include positioningan electrode of a lead based at least in part on the determined leadroll (e.g., to be directed toward or away from tissue such as nervetissue, damaged myocardium, etc.).

FIG. 8 shows an exemplary lead 800 with twist tracking features as wellas an exemplary method 850 for determining twist. The lead 800 includesa distal pair of electrodes 820 and a proximal pair of electrodes 840.As the lead 800 is resilient, its body may twist such that a rolldifferential exists between the distal pair 820 and the proximal pair840. In this example, two local coordinate systems may be defined, onefor each of the electrode pairs 820, 840. Even where the lead 800remains at a particular point in the body (e.g. tip position), rotationor twist may be tracked with respect to a clinician's actions or withrespect to body actions or function.

The exemplary method 850 includes a positioning block 852 where aclinician positions a lead such as the lead 800 in a patient's body. Forexample, the clinician may position a lead in a patient where the leadhas a longitudinal axis that extends from a proximal end to a distal endand where the lead includes electrodes where at least two electrodeshave an electrical center offset from the longitudinal axis of the leadbody. After or during positioning, in a measurement block 854, theclinician instructs a localization system to measure electricalpotential in a three-dimensional potential field using the at least twoelectrodes. In a determination block 856, a localization systemdetermines, based on measured electrical potential and the offsets ofthe electrical centers, local lead roll and lead twist about thelongitudinal axis of the lead body (e.g., in degrees, radians, etc.).

FIG. 9 shows various views of a conventional ring electrode 910 and anexemplary pair of electrodes 930. These views further demonstrate howelectrical centers vary or do not vary with respect to electrodecharacteristics. As shown, the conventional ring electrode 910 has anelectrical center along a central axis of rotation. A view along thisaxis shows the electrical center of the ring electrode 910 centered suchthat rotation about the axis does not result in displacement of itselectrical center from the axis. Further, rotation of the ring electrode910 about its geometric center does not result in displacement of itselectrical center.

In contrast, each of the individual electrodes of the pair 930 has anelectrical center offset from a central axis (e.g., z-axis). A viewalong this axis shows the two distinct electrical centers. Furtherrotation about the geometric center of the pair of electrodes 930results in displacement of each electrical center.

Given the foregoing discussion of coordinate systems and electricalcenters, various exemplary electrodes are shown in FIGS. 10 and 11 asbeing part of a lead. Specifically, FIG. 10 shows exemplary electrodeconfigurations 1010, 1020, and 1030 and FIG. 11 shows exemplaryelectrode configurations 1040 and 1050. Such arrangements may includeone or more circuits such as the circuit 168 of the lead 160 of FIG. 1(e.g., to select or otherwise control an electrode configuration).

The configuration 1010 includes a lead body 1012 and two series ofelectrodes 1014, 1016 where each series includes individually selectablering electrodes 1018. Each of the series of electrodes 1014, 1016 may beformed by splitting, perpendicular to the lead body axis, a singleelectrode such that it resembles two or more rings arranged end-to-endlengthwise.

The configuration 1010 may be used as a marquee whereby a localizationsystem successively displays a position for each individual ring in aseries. Thus, the display would appear as a moving sequence of dots orthe like progressing along the axis of the lead body 1012 (e.g., asuccessive series of markers). When the direction is known (e.g., fromproximal to distal), a clinician can readily ascertain the orientationof the lead body 1012. Further, the localization system may displaycolors or other indicia to indicate a corresponding direction (e.g.,vector). For example, a red vector may indicate a direction “into” adisplay pane (e.g., away from an observer) while a blue vector mayindicate a direction “out of” a display pane (e.g., toward an observer).Yet further, where the series 1014, 1016 are spaced at some distance,the localization system may display colors or other indicia to same oropposing directions. As described herein, an exemplary method mayinclude altering a color of the lead direction marquee, for example,based on direction of the lead direction marquee with respect to acoordinate system (e.g., a coordinate system that corresponds tophysiology of the heart, a patient's body, etc.).

The configuration 1020 includes a lead body 1022 and two series ofelectrodes 1024, 1026 where each series includes individually selectablearc section electrodes 1028. Each of the series of electrodes 1024, 1026may be formed by splitting a single electrode such that it resembles twoor more arced sections arranged circumferentially. For example, the lead160 of FIG. 1 includes electrodes 163, which are arrangedcircumferentially about a lead body. As mentioned, various exemplaryleads may include one or more circuits for control of one or moreelectrodes in an electrode array (see, e.g., the circuit 168 of the lead160 of FIG. 1).

The configuration 1030 includes a lead body 1032 and two sets ofelectrodes 1034, 1036 where each set includes individually selectablecylindrical section electrodes 1038. Each set of electrodes 1034, 1036may be formed by splitting a single electrode such that it resembles twocylindrical sections with an axial offset along the split boundary. Suchan electrode set was described with respect to FIG. 9 (see electrodes930), specifically to explain electrical centers. As shown in FIG. 10,each set has circumferential and axial features. In a particularexample, each set 1034, 1036 can include two or more interlocking piecesthat can form a complete ring, which may be referred to as aninterlocking arrangement.

The configuration 1040 includes a lead body 1042 and two sets ofelectrodes 1044, 1046 where each set includes individually or groupselectable electrodes 1048 arranged circumferentially. Each set ofelectrodes 1044, 1046 is optionally formed by a group of conductorswhere each conductor is attached to or forms an exposed end surfacealong the lead body 1042 arranged circumferentially that, when takentogether, resemble a ring. In FIG. 11, the configuration 1040 may bereferred to as a tiled arrangement.

The configuration 1050 includes a lead body 1052 and two sets ofelectrodes 1054, 1056 where each set includes individually or groupselectable electrodes 1058 arranged circumferentially and axially in ahelix or spiral fashion. Each set of electrodes 1054, 1056 is optionallyformed by a group of conductors where each conductor is attached to orforms an exposed end surface along the lead body 1052 arrangedcircumferentially and axially that, when taken together, resemble aring. In FIG. 11, the configuration 1050 may be referred to as a spiralarrangement.

In the examples of FIGS. 10 and 11, the electrode sets may be (e.g., forpurposes of cardiac study and therapy), approximately 0.3 mm toapproximately 4.0 mm in diameter and approximately 0.5 mm toapproximately 2.5 mm in length.

FIG. 12 shows exemplary electrodes configurations 1210, 1220, which aresuitable for determination of local field heterogeneities. Theconfigurations 1210, 1220 include one or more split-ring electrodes. Asdescribed herein, a circumferential arrangement or a combination ofcircumferential and axial arrangements are particularly suited todetermining local field heterogeneities.

The configuration 1210 includes a lead body 1212 and two sets ofelectrodes 1214, 1216 where each set includes individually or groupselectable electrodes arranged circumferentially and axially. Each setof electrodes 1214, 1216 has one or more associated conductors forelectrodes of proximal, middle, and distal portions. In the example ofFIG. 12, the proximal and distal portions cover the completecircumference of the lead body 1212 and the middle portion (e.g.,portion 1218) is subdivided into three or more portions about thecircumference of the lead body 1212.

The configuration 1220 includes a lead body 1222 and two sets ofelectrodes 1224, 1226 where each set includes individually or groupselectable electrodes arranged circumferentially and axially. Each setof electrodes 1224, 1226 has one or more associated conductors forelectrodes of proximal and distal portions. In the example of FIG. 12,the proximal and distal portions are subdivided in two or morecircumferential portions that are staggered with respect to one another(see, e.g., cross-section of electrode 1228).

As described herein, since distance between electrode portions in eachdirection in local lead or catheter coordinates is known and typicallyfixed, the corresponding distance measured in localization systemcoordinates (e.g., ENSITE® NAVX® system 3D field coordinates) can beused to define a local field scaling factor.

FIG. 13 shows various exemplary methods and displays using alocalization system 1300. The heart 102 is shown with a rightventricular lead 1308 and a left ventricular lead 1306 with a guidancecatheter 1315. The right ventricular lead 1308 includes a pair ofelectrodes 1330 having electrical centers offset from a longitudinalaxis of the lead body and a tip electrode with a screw or helix 1328 forattachment to the myocardium. The left ventricular lead includes aseries of electrodes 1323 with a combination of marquee electrodes (see,e.g., electrodes 1010 of FIG. 10) and interlocking electrodes (see,e.g., electrodes 1030 of FIG. 10).

In the example of FIG. 13, a catheter or sheath 1315 is used forplacement of the left ventricular lead 1306. The catheter 1315 includesa pair of electrodes 1317 having electrical centers offset from alongitudinal axis of the catheter 1315.

A localization system 1380 is configured via a switching module 1384 toacquire information from the various electrodes, configured via acompensation module 1386 to compensate for field heterogeneity andconfigured via a display module 1388 to generate data suitable fordisplay on a monitor, screen, etc. As described herein, a localizationsystem may include an integral display (e.g., as part of a console ornotebook like arrangement) or may include memory to store data suitablefor display (e.g., in a graphics buffer). A localization systemtypically includes one or more graphics processors (e.g., a graphicsaccelerator card, display adapter, etc.) configured for generatingmultidimensional graphics data that can be rendered on a display forviewing by a clinician. Communication between a localization system anda display may occur via wire or wirelessly or via a combination of bothwire and wireless communication. Data may also be stored to a storagedevice and then loaded to a system for display. The display module 1388includes software or hardware and software for generating data suitablefor display on a monitor, screen, etc.

An exemplary RV lead display 1392 based on data generated by the displaymodule 1388 shows a graphic of electrical centers of the electrodes 1330with respect to the tip electrode screw 1328. Insertion of the tipelectrode screw 1328 may be achieved in any of a variety of manners. Forexample, a stylet may be inserted in a lumen of the RV lead 1308 androtated to rotate the tip electrode screw 1328 (e.g., clockwise,counter-clockwise or both clockwise and counter-clockwise). In such anexample, the electrodes 1330 may be tracked to determine if the RV lead1308 is rotating as the stylet is rotated. Further, the localizationsystem 1380 may track the axial distance (e.g., in a local coordinatesystem) between the electrodes 1330 and the tip electrode screw 1328 asthe tip electrode screw 1328 is inserted into the myocardium. Thedisplay 1392 may indicate the axial distance as a displacement that aclinician may track during an implant procedure.

An exemplary sheath display 1394 based on data generated by the displaymodule 1388 shows an angle of rotation offset between the catheter orsheath 1315 and the LV lead 1306. The display 1394 also shows an outlineof the ostium of the coronary sinus as an anatomical reference for aclinician. In such an example, a clinician may seek to avoid binding ofthe LV lead 1306 in the sheath 1315 as the LV lead 1306 is positioned ina vein. Such a display can track total rotation (e.g., beyond 360degrees) and account for positive and negative rotation whether stemmingfrom the sheath 1315 or the LV lead 1306. In the example of FIG. 13, therotation of the LV lead 1306 may be inferred by information acquired viathe series of electrodes 1323 or other electrodes or proximal endinformation (e.g., an end manipulated by a clinician) or a combinationof such aforementioned information.

An exemplary LV lead display 1396 based on data generated by the displaymodule 1388 shows a marquee for the series of electrodes 1323 along witha rotation graphic. In combination, a clinician can readily ascertaindirection and orientation of the distal portion of the lead 1306. In theexample of FIG. 13, the display 1396 includes a marquee speed indicator,which may correspond to a sampling speed for all or certain electrodesof the series 1323. The localization system 1380 may be configured toreceive input from a clinician to control the marquee speed, which canfacilitate placement of a lead (e.g., to coordinate with speed or timingof a clinician's hand or control movements).

In the example of FIG. 13, the display 1396 pertains to navigating alead in a secondary or tertiary branch of the coronary venous system(e.g., tributaries to the coronary sinus). As described herein, theexemplary display 1396 may be applied for display of orientation of alead or catheter tip, for example, while delivering an active fixationlead or while ablating cardiac or other tissue.

As described herein, an exemplary method can acquire positioninformation using an exemplary lead and determine instantaneous tangentdirection along the lead. Such information may be used to accuratelyrender representations of lead bodies on a localization system monitor.In various situations, instantaneous tangent direction along a lead bodymay be used to determine local myocardial performance (e.g., for CRToptimization).

With respect to a lead that includes a helix (e.g., as an anchoringscrew or mechanism), a keyed-tip stylet or a “helix extender” tool(e.g., a piece that clips onto proximal pin and rotates) may be used todeploy a helix without rotating a lead. Alternatively, a lead could berotated if a helix portion were already extended, for example, to screwa fixed helix into tissue. Various active-fixation leads include a helixthat can extend and retract. An exemplary arrangement can include a leadbody with an electrode having an electrical center offset from thelongitudinal axis of the lead body, which would allow for determinationsas to orientation of the lead body. An exemplary arrangement may includea marquee array to determine how far a helix has been extended (e.g.,where the further the helix is extended, the more distal the electricalcenter has moved from another electrode on a known location near thedistal portion of the lead, for example, an active “mapping collar”).For a helix that rotates, either independently during deployment or aspart of the overall lead rotation of a fixed-helix lead, an exemplaryarrangement may allow for an electrical center of the helix to beslightly offset from the longitudinal axis due to the fact that the mostdistal “turn” of the helix comes to a point and does not complete 360degrees. While such a offset of an electrical center may be small, alocalization system may have sufficient resolution and accuracy todistinguish the offset (e.g., optionally differentially with respect tofrom a full cylindrical marker).

FIG. 14 shows an exemplary localization system 1400, an exemplary method1470 and an exemplary data entry sequence 1490. The localization system1400 includes an electrode/lead reference information module 1410, aswitching module 1430 and a display module 1450. The module 1410 mayaccess one or more databases that contain information as to electrodes,leads, combinations of leads and electrodes suitable for use withfeatures of the localization system 1400.

Specifically, the localization system 1400 may access information abouta lead and determine, based on characteristics of the lead, how the leadmay be used with respect to various hardware, software or hardware andsoftware features of the localization system 1400. The module 1410 mayinclude instructions to identify a lead and its electrode type or typesupon connection to the localization system 1400. Such a process may bereferred to as lead or electrode discovery and can rely on informationsuch as impedance, resistance, number of conductors, a lead's built incircuitry (e.g., an ASIC), etc.

In the example of FIG. 14, the switching module 1430 provides varioustypes of switching schemes, which may be suited to particularcharacteristics of a lead or electrodes, including the type of clinicalprocedure. For example, as described with respect to FIG. 13, a screw inprocedure for anchoring a lead (see, e.g., RV lead display 1392) isdifferent than a navigation procedure (see, e.g., LV lead display 1396).Thus, the switching module 1430 may include a table or other datastructure or algorithm that associates various factors to presentsuitable switching schemes for user selection. Alternatively, theswitching module 1430 may automatically select a switching scheme giveninformation about a lead and its electrodes.

The display module 1450 includes various algorithms for generating datasuitable for display. In the example of FIG. 14, the localization system1400 may select a display algorithm based on a selected switchingscheme. For example, given a switching scheme for anchoring, the displaymodule 1450 may select an algorithm that generates data for display of amyocardial boundary and a screw. As position information is acquired,the module 1450 may update the location and rotational position of thescrew with respect to the myocardial boundary.

The exemplary method 1470 may be implemented using a localization systemwith the modules 1430 and 1450. The method 1470 commences in an entryblock 1472 where electrode/lead information is entered, for example, perthe various manners discussed above. In a particular example, aclinician may enter such information via an input device (e.g.,keyboard, touch screen, microphone, mouse, etc.). In a selection block1474, a clinician selects an appropriate switching scheme from one ormore available switching schemes. In another selection block 1476, theclinician selects an appropriate display scheme from one or moreavailable display schemes. The order of the blocks 1474 and 1476 may bereversed or may occur simultaneously (e.g., where display infersswitching or where switching infers display).

Once appropriate information has been entered and selections made, themethod 1470, in an acquisition block 1478, acquires potentials using theelectrodes according to the selected switching scheme. A generationblock 1480 follows that generates data based on the acquired potentialsaccording to the selected display scheme. Upon display of the data,along with corresponding graphics, in an action block 1482, a clinicianmay take appropriate actions. For example, a clinician may navigate thelead, anchor a lead, conduct tests, etc.

The exemplary data entry sequence 1490 demonstrates how and the type ofinformation a clinician may enter while using a localization systemoperating according to the method 1470. In first entry block 1492, aclinician enters information to notify the localization system that aseries of marquee electrodes will be used on a LV lead. In a secondentry block 1494, the clinician selects a switching scheme for fourmarquee electrodes. In a third entry block 1496, the clinician selects adisplay scheme that will display the marquee with anelectrode-to-electrode frequency of 20 Hz (e.g., marquee display rate)and with blue and red vectors or colors to indicate whether the marqueeis “pointing” out of the display screen or into the display screen.

As described herein, switching may not be required depending on howelectrodes of a lead are configuration for electrical connection to alocalization system. Further, an exemplary lead may include a dataacquisition system and communication system that can communicateacquired data via a data bus, which may be wired or wireless. Forexample, a lead may include a head-end (e.g., proximal end) A/D, databuffer and communication circuit that can communicate acquired potentialdata to a localization system. In such an example, the localizationsystem merely receives the data and displays the data according to anappropriate display scheme.

In various examples, a connection scheme exists where electrodes of alead are electrically connected via one or more conductors to alocalization system. For example, a particular arrangement may includeindependent conductors connected to each portion of a split-ringelectrode where each of the conductors is connected to a separatechannel of a localization system.

A localization system can include a module for setup where an electrodearrangement is defined as axial, circumferential, interlocking, tiled,etc. and position of any composite electrode (e.g., ring, spiral orother) may be optionally computed and displayed as an average of each ofits constituent electrode portions. Enhanced tracking features may becomputed by a module by combining appropriate signals in sequence.

In another exemplary connection scheme, each portion of a split-ringelectrode arrangement has an independent conductor, each of which isconnected to a multiplexing unit (MUX), the output of which connects toa single channel of a localization system. The multiplexing unit may(e.g., via software, hardware or hardware and software) combine variouselectrodes or electrode portions and transmit one or more resultantsignals to a localization system. In such a scheme, signals transmittedto the localization system may be perceived as only a single electrode(e.g., where some form of enhanced tracking has already been embedded bythe multiplexing unit).

In another exemplary connection scheme, portions of a split-ringelectrode arrangement are connected distally by a chip (e.g., chip-basedcircuitry such as an ASIC) that performs the multiplexing and a singleconductor carries the signal to a connection with the localizationsystem. In this example, the chip carries out the switching scheme, asappropriate, for desired enhanced localization functionality.

In another exemplary connection scheme, all portions of a split-ringelectrode arrangement are connected to terminals of a multi-terminalhardware switch such as a reed switch or some other electrically,magnetically, or mechanically activated switch. In such an arrangement,an additional patch or other device connected to a localization systemcan activate the switch sequentially to achieve the desired enhancedfunction.

With respect to exemplary switching schemes, a scheme can be programmedto constantly track a distal-most electrode of an arrangement ofelectrodes and sequentially join (e.g., in series) other electrodes ofthe arrangement, one or more at a time, from proximal to distal. Forexample, in an axial arrangement containing five electrodes, where themost distal electrode is denoted “A” and the most proximal electrode isdenoted “E”, a switching scheme may select the following electrodecombinations: “AE-AD-AC-AB-AE-AD-AC-AB . . . .” Alternatively, the mostdistal need not always be switched on, but rather simply switchsequentially from most proximal to most distal, for example:“E-D-C-B-A-E-D-C-B-A . . . .” Alternatively, the distal electrode may bealways switched on, and the scheme programmed to simply turn one or moreproximal electrodes on and off sequentially, for example:“AB-A-AB-A-AB-A . . . .” Such a scheme generates an effect of moving the“center of gravity” of the electrode arrangement from proximal todistal. Information acquired according to such a scheme may be displayedon a monitor as an electrode travelling slightly from proximal to distalalong the axial direction (e.g., a marquee effect).

Various exemplary schemes can with electrodes at or near the distal endof a lead can distinguish whether the distal end is pointed tangentialor perpendicular to the heart surface, for example, where a localizationsystem is used to fix a lead at a particular location (such as HISbundle). Further, such a scheme can determine which direction a lead orcatheter is pointed as it reaches a branch point in the coronary venoussystem. With respect to pacing therapies, such an approach can aidsub-branch selection in placement of a pacing lead.

An exemplary scheme can track electrodes of a lead that are locatedalong a lead body (e.g., at a distance from a distal end of more than acentimeter) to more accurately determine the trajectory of the leadbody. For example, based on direction that an electrode is pointing, alocalization system can use not only the position but also tangentdirection in a polynomial or spline calculation to draw a representationof the lead body. An exemplary method can track changes in directionthroughout a cardiac cycle to yield valuable information about cardiacrotation. Such information may be used for CRT optimization.

Various exemplary techniques described herein may be applied toscenarios where other types of imaging leads or catheters are used(e.g., fiber-optic, ultrasound, or other modalities). For example, insuch a scenario, a localization system can acquire information anddetermine what direction an imaging lead is pointing, which can help tooptimize image acquisition. Such techniques can aid imaging modalitiesthat rely on Doppler methods or backscatter, especially those that mayrequire parallel or perpendicular orientations for the most accurateresults.

As described herein, various exemplary electrodes may be used todetermine local deformation gradient. For example, a circumferential orinterlocking arrangement may be used with an independent-channelconnection to a localization system to acquire information forobservation of motion as to local deformation. In contrast, for asingle, solid electrode, only the extent of average motion in the(x,y,z) Cartesian field can be determined. By observing differentialmotion of each portion of an exemplary electrode arrangement, not only(x,y,z) components but also rotation about the lead axis and tilt of thecatheter axis can be determined. Such detailed motion information can beplugged into a deformation tensor computed for tissue next to theelectrode arrangement, yielding valuable information about the localtissue mechanical performance. Such information can be used inconjunction with various CRT optimization schemes.

Exemplary External Programmer

FIG. 15 illustrates pertinent components of an external programmer 1500for use in programming an implantable medical device 100 (see, e.g.,FIGS. 1 and 2). The external programmer 1500 optionally receivesinformation from other diagnostic equipment 1650, which may be acomputing device capable of acquiring motion information related tocardiac mechanics. For example, the equipment 1650 may include acomputing device to deliver current and to measure potentials using avariety of electrodes including at least one electrode positionable inthe body (e.g., in a vessel, in a chamber of the heart, within thepericardium, etc.). Equipment may include a lead for chronicimplantation or a catheter for temporary implantation in a patient'sbody. Equipment may allow for acquisition of respiratory motion and aidthe programmer 1500 in distinguishing respiratory motion from cardiac.

Briefly, the programmer 1500 permits a clinician or other user toprogram the operation of the implanted device 100 and to retrieve anddisplay information received from the implanted device 100 such as IEGMdata and device diagnostic data. The programmer 1500 may also instruct adevice or diagnostic equipment to deliver current to generate one ormore potential fields within a patient's body where the implantabledevice 100 may be capable of measuring potentials associated with thefield(s).

The external programmer 1500 may be configured to receive and displayECG data from separate external ECG leads 1732 that may be attached tothe patient. The programmer 1500 optionally receives ECG informationfrom an ECG unit external to the programmer 1500. The programmer 1500may use techniques to account for respiration.

Depending upon the specific programming, the external programmer 1500may also be capable of processing and analyzing data received from theimplanted device 100 and from ECG leads 1732 to, for example, renderdiagnosis as to medical conditions of the patient or to the operationsof the implanted device 100. As noted, the programmer 1500 is alsoconfigured to receive data representative of conduction time delays fromthe atria to the ventricles and to determine, therefrom, an optimal orpreferred configuration for pacing. Further, the programmer 1500 mayreceive information such as ECG information, IEGM information,information from diagnostic equipment, etc., and determine one or moremetrics for optimizing therapy.

Considering the components of programmer 1500, operations of theprogrammer are controlled by a CPU 1702, which may be a generallyprogrammable microprocessor or microcontroller or may be a dedicatedprocessing device such as an application specific integrated circuit(ASIC) or the like. Software instructions to be performed by the CPU areaccessed via an internal bus 1704 from a read only memory (ROM) 1706 andrandom access memory 1730. Additional software may be accessed from ahard drive 1708, floppy drive 1710, and CD ROM drive 1712, or othersuitable permanent or removable mass storage device. Depending upon thespecific implementation, a basic input output system (BIOS) is retrievedfrom the ROM 1706 by CPU 1702 at power up. Based upon instructionsprovided in the BIOS, the CPU 1702 “boots up” the overall system inaccordance with well-established computer processing techniques.

Once operating, the CPU 1702 displays a menu of programming options tothe user via an LCD display 1614 or other suitable computer displaydevice. To this end, the CPU 1702 may, for example, display a menu ofspecific programming parameters of the implanted device 100 to beprogrammed or may display a menu of types of diagnostic data to beretrieved and displayed. In response thereto, the clinician entersvarious commands via either a touch screen 1616 overlaid on the LCDdisplay or through a standard keyboard 1618 supplemented by additionalcustom keys 1620, such as an emergency VVI (EVVI) key. The EVVI key setsthe implanted device to a safe VVI mode with high pacing outputs. Thisensures life sustaining pacing operation in nearly all situations but byno means is it desirable to leave the implantable device in the EVVImode at all times.

With regard to mapping of metrics (e.g., for patterns of conduction),the CPU 1702 includes a 3-D mapping system 1747 and an associated dataanalysis system 1749. The systems 1747 and 1749 may receive positioninformation and physiological information from the implantable device100 and/or diagnostic equipment 1650. The data analysis system 1749optionally includes control logic to associate information and to makeone or more conclusions based on metrics, for example, as indicated inFIG. 3 to optimize delivery of therapy (e.g., to optimize a pacingconfiguration).

Where information is received from the implanted device 100, a telemetrywand 1728 may be used. Other forms of wireless communication exist aswell as forms of communication where the body is used as a “wire” tocommunicate information from the implantable device 100 to theprogrammer 1500.

If information is received directly from diagnostic equipment 1650, anyappropriate input may be used, such as parallel 10 circuit 1740 orserial 10 circuit 1742. Motion information received via the device 100or via other diagnostic equipment 1650 may be analyzed using the mappingsystem 1747. In particular, the mapping system 1747 (e.g., controllogic) may identify positions within the body of a patient and associatesuch positions with one or more electrodes where such electrodes may becapable of delivering stimulation energy to the heart, performing otheractions or be associated with one or more sensors.

A communication interface 1745 optionally allows for wired or wirelesscommunication with diagnostic equipment 1650 or other equipment (e.g.,equipment to ablate or otherwise treat a patient). The communicationinterface 1745 may be a network interface connected to a network (e.g.,intranet, Internet, etc.).

A map or model of cardiac information may be displayed using display1614 based, in part, on 3-D heart information and optionally 3-D torsoinformation that facilitates interpretation of information. Such 3-Dinformation may be input via ports 1740, 1742, 1745 from, for example, adatabase, a 3-D imaging system, a 3-D location digitizing apparatus(e.g., stereotactic localization system with sensors and/or probes)capable of digitizing the 3-D location. While 3-D information andlocalization are mentioned, information may be provided with fewerdimensions (e.g., 1-D or 2-D). For example, where motion in onedimension is insignificant to one or more other dimensions, then fewerdimensions may be used, which can simplify procedures and reducecomputing requirements of a programmer, an implantable device, etc. Theprogrammer 1500 optionally records procedures and allows for playback(e.g., for subsequent review). For example, a heart map and all of theelectrical activation data, mechanical activation data, etc., may berecorded for subsequent review, perhaps if an electrode needs to berepositioned or one or more other factors need to be changed (e.g., toachieve an optimal configuration). Electrodes may be lead based ornon-lead based, for example, an implantable device may operate as anelectrode and be self powered and controlled or be in a slave-masterrelationship with another implantable device (e.g., consider a satellitepacemaker, etc.). An implantable device may use one or more epicardialelectrodes.

Once all pacing leads are mounted and all pacing devices are implanted(e.g., master pacemaker, satellite pacemaker, biventricular pacemaker),the various devices are optionally further programmed.

The telemetry subsystem 1722 may include its own separate CPU 1724 forcoordinating the operations of the telemetry subsystem. In a dual CPUsystem, the main CPU 1702 of programmer communicates with telemetrysubsystem CPU 1724 via internal bus 1704. Telemetry subsystemadditionally includes a telemetry circuit 1726 connected to telemetrywand 1728, which, in turn, receives and transmits signalselectromagnetically from a telemetry unit of the implanted device. Thetelemetry wand is placed over the chest of the patient near theimplanted device 100 to permit reliable transmission of data between thetelemetry wand and the implanted device.

Typically, at the beginning of the programming session, the externalprogramming device 1500 controls the implanted device(s) 100 viaappropriate signals generated by the telemetry wand to output allpreviously recorded patient and device diagnostic information. Patientdiagnostic information may include, for example, motion information(e.g., cardiac, respiratory, etc.) recorded IEGM data and statisticalpatient data such as the percentage of paced versus sensed heartbeats.Device diagnostic data includes, for example, information representativeof the operation of the implanted device such as lead impedances,battery voltages, battery recommended replacement time (RRT) informationand the like.

Data retrieved from the implanted device(s) 100 can be stored byexternal programmer 1500 (e.g., within a random access memory (RAM)1730, hard drive 1708, within a floppy diskette placed within floppydrive 1710). Additionally, or in the alternative, data may bepermanently or semi-permanently stored within a compact disk (CD) orother digital media disk, if the overall system is configured with adrive for recording data onto digital media disks, such as a write onceread many (WORM) drive. Where the programmer 1500 has a communicationlink to an external storage device or network storage device, theninformation may be stored in such a manner (e.g., on-site database,off-site database, etc.). The programmer 1500 optionally receives datafrom such storage devices.

A typical procedure may include transferring all patient and devicediagnostic data stored in an implanted device 100 to the programmer1500. The implanted device(s) 100 may be further controlled to transmitadditional data in real time as it is detected by the implanteddevice(s) 100, such as additional motion information, IEGM data, leadimpedance data, and the like. Additionally, or in the alternative,telemetry subsystem 1722 receives ECG signals from ECG leads 1732 via anECG processing circuit 1734. As with data retrieved from the implanteddevice 100, signals received from the ECG leads are stored within one ormore of the storage devices of the programmer 1500. Typically, ECG leadsoutput analog electrical signals representative of the ECG. Accordingly,ECG circuit 1734 includes analog to digital conversion circuitry forconverting the signals to digital data appropriate for furtherprocessing within programmer 1500. Depending upon the implementation,the ECG circuit 1743 may be configured to convert the analog signalsinto event record data for ease of processing along with the eventrecord data retrieved from the implanted device. Typically, signalsreceived from the ECG leads 1732 are received and processed in realtime.

Thus, the programmer 1500 is configured to receive data from a varietyof sources such as, but not limited to, the implanted device 100, thediagnostic equipment 1650 and directly or indirectly via external ECGleads (e.g., subsystem 1722 or external ECG system). The diagnosticequipment 1650 includes wired 1654 and/or wireless capabilities 1652which optionally operate via a network that includes the programmer 1500and the diagnostic equipment 1650 or data storage associated with thediagnostic equipment 1650.

Data retrieved from the implanted device(s) 100 typically includesparameters representative of the current programming state of theimplanted devices. Under the control of the clinician, the externalprogrammer displays the current programming parameters and permits theclinician to reprogram the parameters. To this end, the clinician entersappropriate commands via any of the aforementioned input devices and,under control of CPU 1702, the programming commands are converted tospecific programming parameters for transmission to the implanted device100 via telemetry wand 1728 to thereby reprogram the implanted device100 or other devices, as appropriate.

Prior to reprogramming specific parameters, the clinician may controlthe external programmer 1500 to display any or all of the data retrievedfrom the implanted device 100, from the ECG leads 1732, includingdisplays of ECGs, IEGMs, statistical patient information (e.g., via adatabase or other source), diagnostic equipment 1650, etc. Any or all ofthe information displayed by programmer may also be printed using aprinter 1736.

A wide variety of parameters may be programmed by a clinician. Inparticular, for CRT, the AV delay and the VV delay of the implanteddevice(s) 100 are set to optimize cardiac function. In one example, theVV delay is first set to zero while the AV delay is adjusted to achievethe best possible cardiac function, optionally based on motioninformation. Then, VV delay may be adjusted to achieve still furtherenhancements in cardiac function.

Programmer 1500 optionally includes a modem to permit directtransmission of data to other programmers via the public switchedtelephone network (PSTN) or other interconnection line, such as a T1line or fiber optic cable. Depending upon the implementation, the modemmay be connected directly to internal bus 1704 may be connected to theinternal bus via either a parallel port 1740 or a serial port 1742.

Other peripheral devices may be connected to the external programmer viathe parallel port 1740, the serial port 1742, the communicationinterface 1745, etc. Although one of each is shown, a plurality of inputoutput (IO) ports might be provided. A speaker 1744 is included forproviding audible tones to the user, such as a warning beep in the eventimproper input is provided by the clinician. Telemetry subsystem 1722additionally includes an analog output circuit 1746 for controlling thetransmission of analog output signals, such as IEGM signals output to anECG machine or chart recorder.

With the programmer 1500 configured as shown, a clinician or other useroperating the external programmer is capable of retrieving, processingand displaying a wide range of information received from the ECG leads1732, from the implanted device 100, the diagnostic equipment 1650,etc., and to reprogram the implanted device 100 or other implanteddevices if needed. The descriptions provided herein with respect to FIG.15 are intended merely to provide an overview of the operation ofprogrammer and are not intended to describe in detail every feature ofthe hardware and software of the device and is not intended to providean exhaustive list of the functions performed by the device 1500. Otherdevices, particularly computing devices, may be used.

CONCLUSION

Although exemplary methods, devices, systems, etc., have been describedin language specific to structural features and/or methodological acts,it is to be understood that the subject matter defined in the appendedclaims is not necessarily limited to the specific features or actsdescribed. Rather, the specific features and acts are disclosed asexemplary forms of implementing the claimed methods, devices, systems,etc.

What is claimed is:
 1. A system comprising: an implantable lead having atubular body extending from a proximal end to a distal end of theimplantable lead, the tubular body having a longitudinal axis extendingfrom the proximal end to the distal end of the implantable lead, and thetubular body having an outer surface extending from the proximal end tothe distal end of the implantable lead; a pair of interlocking,independent electrodes directly disposed on the surface of the tubularbody, wherein each of the electrodes comprises an electrical centeroffset from the longitudinal axis of the tubular body; control logic toselect one or both of the electrodes; control logic to measureelectrical potential in a three-dimensional potential field using aselected electrode or selected electrodes; and control logic to generatedata, based at least in part on measurement of electrical potential, fordisplay of the electrical center for each of the electrodes; whereineach of the electrodes comprises a substantially cylindrical portionadjacent a semi-cylindrical portion wherein the semi-cylindrical portionoffsets the electrical center toward the semi-cylindrical portion. 2.The system of claim 1, wherein the control logic to generate datafurther comprises control logic to generate one or more indicators oforientation for an electrical center about the longitudinal axis of thetubular body.
 3. The system of claim 1, further comprising an angle asan indicator of orientation.
 4. The system of claim 1, furthercomprising an anatomical direction as an indicator of orientation. 5.The system of claim 1, wherein the control logic to generate datafurther comprises control logic to generate an indicator of axialdistance between the electrical centers along the longitudinal axis ofthe tubular body.
 6. The system of claim 1, wherein the control logic tomeasure comprises control logic of a localization system configured togenerate the three dimensional potential field.
 7. The system of claim1, further comprising a switching mechanism.
 8. The system of claim 7,wherein the implantable lead comprises the switching mechanism.
 9. Thesystem of claim 7, wherein a localization system comprises the switchingmechanism.
 10. The system of claim 1, further comprising control logicto render the generated data to a display.
 11. The system of claim 1,further comprising a display.
 12. The system of claim 1, wherein each ofthe electrodes has an outer surface and an inner surface, wherein theinner surface of each of the electrodes directly contacts the outersurface of the tubular body.
 13. The system of claim 1, wherein each ofthe electrodes has an outer surface and an inner surface, wherein theinner surface of each of the electrodes is directly secured to the outersurface of the tubular body.
 14. The system of claim 1, furthercomprising a lumen disposed within the tubular body, the lumen suitablefor receipt of a guidewire to facilitate placement of the implantablelead.
 15. The system of claim 1, further comprising a stimulationdevice, wherein the proximal end of the tubular body is connected to thestimulation device.
 16. The system of claim 1, wherein the surface ofthe tubular body comprises an electrically insulative material.
 17. Thesystem of claim 16, wherein the electrodes remain stationary relative tothe tubular body.
 18. A system comprising: an implantable lead having atubular body, the tubular body having a longitudinal axis extending fromthe proximal end to the distal end of the implantable lead; a pair ofinterlocking, independent electrodes directly disposed on the tubularbody, wherein each of the electrodes comprises an electrical centeroffset from the longitudinal axis of the tubular body; control logic toselect one or both of the electrodes; control logic to measureelectrical potential in a three-dimensional potential field using aselected electrode or selected electrodes; and control logic to generatedata, based at least in part on measurement of electrical potential, fordisplay of the electrical center for each of the electrodes; whereineach of the electrodes comprises a substantially cylindrical portionadjacent a semi-cylindrical portion wherein the semi-cylindrical portionoffsets the electrical center toward the semi-cylindrical portion.
 19. Asystem comprising: an implantable lead body having a longitudinal axisthat extends from a proximal end to a distal end; a pair ofinterlocking, independent electrodes disposed on the implantable leadbody, wherein each of the electrodes comprises an electrical centeroffset from the longitudinal axis of the implantable lead body; controllogic to select one or both of the electrodes; control logic to measureelectrical potential in a three-dimensional potential field using aselected electrode or selected electrodes; and control logic to generatedata, based at least in part on measurement of electrical potential, fordisplay of the electrical center for each of the electrodes; whereineach of the electrodes comprises a substantially cylindrical portionadjacent a semi-cylindrical portion wherein the semi-cylindrical portionoffsets the electrical center toward the semi-cylindrical portion.